System for the secondary suspension of a superstructure of a rail vehicle having a passive spring element

ABSTRACT

A secondary suspension for a rail vehicle includes a superstructure, a bogie and a steel spring arranged between the superstructure and the bogie. The steel spring ensures at least one raised traveling level for the superstructure when the rail vehicle is traveling. Further included is a tension cylinder. When the rail vehicle is stopped the steel spring is compressed by the tension cylinder to adjust the superstructure to a lowered station platform level below the at least one traveling level.

The present invention relates to a system for the secondary suspension of a superstructure of a rail vehicle, having a steel spring as a passive spring element arranged between the superstructure and a bogie, which steel spring ensures as least one raised traveling level NF for the superstructure when the rail vehicle is traveling.

A secondary suspension between a superstructure and a railborne bogie of a rail vehicle is used particularly for the additional vibration isolation of the superstructure in order to permit a comfortable travel when conveying passengers. In many cases, the secondary suspension also interacts with a roll control for the superstructure. In addition to the secondary suspension used for the increase of comfort, a rail vehicle of the type of interest here also has a primary suspension. The primary suspension acts between the wheel axles of the rail vehicle and the bogie and is used predominantly for absorbing hard shocks to which the rail vehicle is subjected during its travel as a result of an uneven rail guidance and the like.

It is generally known to use conventional steel springs for the secondary suspension in the simplest case, in addition to a pneumatic suspension or hydropneumatic suspension. The superstructure is normally cushioned with respect to the bogie by way of two such passive spring elements, in which case the bogie normally carries a pair of wheel axles which establish the contact with the rail.

However, when a secondary suspension is constructed by means of steel springs as passive spring elements, the problem arises that the superstructure level may change as a function of the loading. In the sense of the present patent application, the superstructure level is the vertical level of the superstructure relative to the bogie or to the ground.

From European Patent Document EP 0 663 877 B1, a system for the secondary suspension is known which avoids this problem in that no steel springs are used for the secondary suspension. On the contrary, the secondary suspension is implemented by way of a hydropneumatic spring unit. The hydropneumatic spring unit consists of a spring leg and of a hydropneumatic pressure accumulator. These assemblies carry out the function of cushioning the superstructure as well as the function of damping the spring excursions. The spring leg is fastened on the superstructure and on the bogie. During a spring excursion, the piston in the spring leg displaces a defined oil volume. In the hydropneumatic pressure accumulator connected with the spring leg, this oil volume acts against a gas cushion which is separated from the oil volume by a membrane and is therefore used as a springy element. The hydraulic fluid as the liquid column therefore takes over the function of the power transmission. Vehicle vibrations during the travel are damped by means of the nozzles housed in a nozzle block. As the load of the superstructure increases, the gas volume in the hydropneumatic accumulators is compressed. Without any level control system, this would result in a lowering of the superstructure, as in the case of the above-described passive spring element. However, in order to avoid this lowering, the reduction of the gas volume has to be compensated by feeding a corresponding amount of hydraulic fluid. For this purpose, the level control system is provided which carries out this compensation as a function of the distance between the superstructure and the bogie measured by means of a level sensor. The controlling of level changes takes place continuously and with little time delay while the vehicle is stopped. During the travel, the mean vehicle level is also continuously monitored and compensated.

In certain application cases, it is defined that, in addition to a raised traveling level N_(F), the superstructure also has to take up a station platform level N_(B) which is below it and which, in a lowered position of the superstructure matches the door steps of the rail vehicles with the height of the station platform, so that an entering and exiting becomes possible without steps. Furthermore, safety-related regulations require that, despite such a lowered station platform level N_(B), in the case of a system failure, the superstructure of the rail vehicle can also independently take up a so-called emergency level N_(N) situated slightly above it. This emergency level in N_(N) situated between the lowered station platform level N_(B) and the raised traveling level N_(F), despite the system failure, permits an at least slow continued traveling of the rail vehicle.

In the case of the known system for the secondary suspension with an active level control, however, an emergency level N_(N) starting from a traveling level N_(F) can only be adjusted when still sufficient stored pressure is present in the supply reservoir and the assigned valve is operated manually. Thus, an emergency level N_(N) cannot be ensured under all conditions.

Furthermore, the known system for the secondary suspension has a fairly high-cost construction, which applies particularly to the construction of the spring leg constructed in the manner of a lifting cylinder.

It is therefore an object of the present invention to provide a system for the secondary suspension which has a simple construction and by means of which, despite a system failure, the superstructure can take up an emergency level N_(N) from a lowered station platform level N_(B) under any condition.

Based on a system according to the preamble of claim 1, this object is achieved in conjunction of its characterizing features. The following dependent claims indicate advantageous further developments of the invention.

The invention includes the technical teaching that a steel spring as a passive spring element of a secondary suspension can be compressed when the rail vehicle is stopped by means of a tension cylinder in order to adjust a lowered station platform level for the superstructure situated below the traveling level N_(F). In this case, the passive spring element is connected parallel to the tension cylinder.

It is an advantage of the solution according to the invention that, in the event of a system failure, the tension cylinder is automatically depressurized so that the parallel steel spring rebounds. During a stoppage, that is, in the area of the station stop, this has the effect that, from the lowered station platform level N_(B), the superstructure arrives at a higher level—which here corresponds to the traveling level N_(F), so that a continued traveling of the rail vehicle becomes possible. The implementation of the solution according to the invention requires only simple construction elements, such as a conventional steel spring as well as a hydraulic cylinder also available as a standardized component.

The tension cylinder should preferably be arranged locally next to the steel spring while acting between the superstructure and the bogie. This arrangement ensures a good access to the tension cylinder as well as to the steel spring from the outside, which is advantageous particularly for servicing or repair. As an alternative, it is also conceivable to arrange the tension cylinder inside the steel spring constructed as a coil spring and acting between the superstructure and the bogie. In comparison to the former arrangement, this has the advantage of a particularly space-saving housing which should be selected when required by a narrow installation situation.

Since the tension cylinder has to follow not only vertical but also transverse and longitudinal movements of the superstructure relative to the bogie, it should be equipped with a ball joint on the bogie side and the superstructure side, whereby the coupling takes place. The ball joint can be constructed either as a conventional ball joint or, in a particularly space-saving manner, as a ball socket, in which case the pivot can be selected as a function of the diameter of the ball socket.

According to a measure improving the invention, a level sensor is provided for measuring the distance between the superstructure and the bogie, which level sensor, as an actual-value generator, is a component of an active level control for adjusting a desired superstructure level. Thus, the traveling level N_(F) as well as station platform level N_(B) can be precisely adjusted by an electronic defining of desired values. A linear distance sensor is, for example, suitable for use as the level sensor. A particularly space-saving arrangement is obtained when the level sensor is integrated directly in the tension cylinder.

As an alternative to this level control, it is also conceivable to achieve a level adjustment of the tension cylinder in that the latter can be moved against a final stop in order to reach the lowered station platform level N_(B). However, care should be taken in that regard that the hydraulic system of the secondary suspension is to be dimensioned such that a stored pressure exists which is sufficient for a complete lowering of the superstructure by means of the tension cylinder.

A hydraulic unit should advantageously be used for admitting pressure to the tension cylinder. The working line of the hydraulic unit leading to the tension cylinder can alternatively be acted upon either by means of a filling valve connected with a pressure source or can be relieved by means of a relief valve connected with a tank, the filling valve and the relief valve being alternately controllable by means of an electronic control unit. In the case of an active level control, the filling valves and the relief valve form the actuators of the control circuit.

In order to prevent a taking-in of hydraulic oil from the tank during the deflection of the steel spring as a result of vibrating movements during the travel, it is suggested that the tension cylinder has a piston which takes along a piston rod originating therefrom only in the moving-in direction, whereas, in the moving-out direction, the piston is uncoupled therefrom. By means of this simple mechanical uncoupling, the disturbing suction intake is reliably avoided.

As an alternative, it is also conceivable to connect a hydraulic accumulator to the working line leading to the tension cylinder. This hydraulic accumulator inserted to this extent into the level circuit permits the regulating of the level also during the travel. During the rebounding, the hydraulic accumulator will then receive the hydraulic oil displaced from the tension cylinder. The filling valve and the relief valve of the hydraulic unit can remain closed during the travel. The above-mentioned hydraulic accumulator is preferably constructed in the manner of a membrane accumulator.

Additional measures improving the invention will be indicated in detail in the following together with the description of a preferred embodiment of the invention by means of the single FIGURE.

The FIGURE is a schematic view of a system for the secondary suspension of a superstructure using a passive spring element.

According to the FIGURE, a steel spring 3 is arranged as a passive spring element between an upper superstructure 1 of a rail vehicle—not shown in detail—and a lower bogie 2. During the travel of the rail vehicle, the steel spring 3 ensures a raised traveling level N_(F) for the superstructure 1, so that the latter remains unaffected by disturbing vibrations caused by the travel. The steel spring 3 simultaneously takes over also the transverse suspension of the superstructure 1. A tension cylinder 4 is connected parallel to the steel spring 3. To this extent, the tension cylinder 4 also acts between the upper superstructure 1 and the lower bogie 2 and is linked thereto. The tension cylinder 4 is used for the compression of the adjacent steel spring 3, so that the superstructure 1 can be changed from its normal traveling level N_(F) to a lowered station platform level N_(B). At this lower station platform level N_(B), the door steps of the entrance doors of the superstructure 1 are coordinated with the station platform—also not shown—with respect to the height, so that an unhindered entering and exiting becomes possible.

For this purpose, pressure is admitted to the tension cylinder 4 by way of a hydraulic unit 5. The hydraulic unit 5 comprises a filling valve 6 as well as a relief valve 7 which can alternately be controlled by way of an electronic control unit—not shown here in detail—. In this embodiment, the filling valve 6 as well as the relief valve 7 are constructed as a spring-restored monostable 2/2-way valve.

On the feeding-pressure side, the filling valve 6 is connected with a first pressure source in the form of a hydraulic pump 8. The hydraulic pump 8 delivers hydraulic fluid from a tank 9 by way of a non-return valve 10 to the filling valve 6 and simultaneously to a first hydropneumatic accumulator 11. Furthermore, a first pressure sensor 12 is provided for monitoring the feeding pressure. By way of the filling valve 6, the feeding pressure arrives in a working line 13 leading to the tension cylinder 4 in order to act upon the tension cylinder 4 so that the superstructure 1 is moved from the traveling level N_(F) to the station platform level N_(B).

A return movement from the station platform level N_(B) to the normal traveling level N_(F) takes place by an opening of the relief valve 7 so that, triggered by the effect of the force of the steel spring 3, the hydraulic fluid escapes from the tension cylinder 4 and, by way of the working line 13 and the opened relief valve 7, returns into the tank 9′. Another pressure sensor 14 is used for monitoring the working pressure existing in the working line 13. In addition, a second hydropneumatic accumulator 15 is connected into working line 13. The hydropneumatic accumulator 15 permits the controlling of the height level of the superstructure 1 during the travel.

The active controlling of the superstructure level is permitted by way of a level sensor 16 which, as an actual value generator, measures the distance between the superstructure 1 and the bogie 3 and transmits the measured value to the electronic control unit—not shown here in detail—. The level sensor 16 is constructed as a so-called linear distance sensor.

If the pressure supply or the electronic control fails in the event of a disturbance, the hydraulic unit 5 is deenergized. The tank-side relief valve 7 takes up its normal-open switching position and establishes the connection to the tank 9′, so that the tension cylinder 4 is depressurized. As a result, the steel spring 3 rebounds, so that the superstructure 1 moves from the station platform level N_(B) to the traveling level N_(F), which in this case is simultaneously the emergency level N_(N).

LIST OF REFERENCE NUMBERS

-   1 Superstructure -   2 bogie -   3 steel spring -   4 tension cylinder -   5 hydraulic unit -   6 filling valve -   7 relief valve -   8 hydraulic pump -   9 tank -   10 non-return valve -   11 first hydropneumatic accumulator -   12 first pressure sensor -   13 working line -   14 second pressure sensor -   15 second hydropneumatic accumulator (with a damping nozzle) -   16 level sensor -   N_(F) traveling level -   N_(N) emergency level -   N_(B) station platform level 

1. A secondary suspension system for a rail vehicle comprising a superstructure; a bogie; a steel spring arranged between the superstructure and the bogie, the steel spring ensuring at least one raised traveling level for the superstructure when the rail vehicle is traveling; a tension cylinder; and when the rail vehicle is stopped the steel spring is compressed by the tension cylinder to adjust the superstructure to a lowered station platform level below the at least one traveling level.
 2. The system according to claim 1, wherein the tension cylinder is arranged locally next to the steel spring and acts between the superstructure and the bogie.
 3. The system according to claim 1, wherein the tension cylinder is arranged inside the steel spring, the steel spring, constructed as a coil spring and acting between the superstructure and the bogie.
 4. The system according to claim 1, further including a level sensor is to measure a distance between the superstructure and the bogie, which level sensor is a component of an active level control for adjusting a desired superstructure level.
 5. The system according to claim 4, wherein the level sensor is constructed as a linear distance sensor.
 6. The system according to claim 1, further including a level sensor constructionally integrated in the tension cylinder.
 7. The system according to claim 1, wherein the tension cylinder, when used as a passive level adjustment, is moved against a final stop in order to reach the lowered station platform level.
 8. The system according to claim 1, further including a hydraulic unit and a working, line connected to the tension cylinder, to admit pressure to the tension cylinder, the hydraulic unit being alternately acted upon by one of the following a) a filling valve connected with at least one pressure source and b) a relief valve connected with a tank, and the filling valve and the relief valve being alternately controllable by an electronic control unit.
 9. The system according to claim 1, wherein the tension cylinder includes a piston having a piston rod originating from the piston, the piston rod being movable relative to the piston during a deflection of the steel spring.
 10. The system according to claim 1, wherein to control the superstructure level during travel of the rail vehicle, a hydropneumatic accumulator is connected to a working line leading to the tension cylinder.
 11. The system according to claim 1, wherein the steel spring is a passive spring element.
 12. The system according to claim 4, wherein the level sensor is an actual value generator. 